Device structure and manufacturing method using HDP deposited source-body implant block

ABSTRACT

This invention discloses a semiconductor power device. The trenched semiconductor power device includes a trenched gate, opened from a top surface of a semiconductor substrate, surrounded by a source region encompassed in a body region near the top surface above a drain region disposed on a bottom surface of a substrate. The semiconductor power device further includes an implanting-ion block disposed above the top surface on a mesa area next to the body region having a thickness substantially larger than 0.3 micron for blocking body implanting ions and source ions from entering into the substrate under the mesa area whereby masks for manufacturing the semiconductor power device can be reduced.

This patent application is a Divisional Application and claims thePriority Date of a co-pending application Ser. No. 13/200,869 filed onOct. 4, 2011 and application Ser. No. 13/200,869 is a DivisionalApplication and claims the Priority of application Ser. No. 11/796,985filed on Apr. 30, 2007 by common Inventors of this Application nowissued into U.S. Pat. No. 8,035,159. The Disclosures made in the patentapplication Ser. Nos. 13/200,869 and 11/796,985 are hereby incorporatedby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to the semiconductor power devices. Moreparticularly, this invention relates to an improved and novelmanufacturing process and device configuration for providing the MOSFETdevice with trench gates having thick bottom trench oxide or split gateby applying high density plasma based manufacturing processes withreduced number of masks.

2. Description of the Related Art

In order to reduce the power consumptions and to increase the switchingspeed of a power semiconductor power device, it is desirable to furtherreduce the gate capacitance. Generally, in a trench gate MOSFET device,a reduced gate capacitance is achieved by forming a thick oxide layer onthe trench bottom of the trench gate. Alternately, the trench gate isformed as a split gate to reduce the gate capacitance. However, in orderto form a thick oxide layer on the trench bottom or a split gate withsplit and mutually insulated bottom and top gate segment in the trenchtypically require additional processing steps. These additionalprocessing steps may adversely affect the device production yields andcosts and further reduce the device reliability due to the potentialerrors that may be introduced in carrying out the more complicatemanufacturing processes.

Therefore, a need still exists in the art of power semiconductor devicedesign and manufacture to provide new manufacturing method and deviceconfiguration in forming the power devices such that the above discussedproblems and limitations can be resolved. It is desirable to simplifythe manufacturing processes in forming the thick oxide layer on thebottom of the trench gate. Alternately, it is further desirable tosimplify the processes in forming the split gate in the trench of asemiconductor power device such that the technical limitations can beresolved.

SUMMARY OF THE PRESENT INVENTION

It is therefore an aspect of the present invention to provide a new andimproved semiconductor power device by applying a new manufacturingmethod that is able to control plasma deposition at target areas. Thisnew HDP deposition method is able to simplify the process by applyingthe high-density plasma (HDP) deposition of thick oxide layer at thetrench bottom such that the formation of the thick oxide layer at thetrench bottom can be significantly simplified and the above-discussedtechnical difficulties can be resolved.

Specifically, it is another aspect of this invention to provide a newand improved semiconductor power device by applying a new manufacturingmethod with a technique to control a high-density plasma deposition(HDP) of insulation layer at predefined targeted areas. This new HDPdeposition method is able to simultaneously deposit a thick oxide layerat the trench bottom and also on the mesa area to serve as an implantmask such the masks required for manufacturing a semiconductor powerdevice is reduced.

Another aspect of this invention is to provide a new and improvedsemiconductor power device by applying a new manufacturing method with atechnique to control a high-density plasma deposition (HDP) ofinsulation layer at predefined targeted areas. This new HDP depositionmethod is able to simultaneously deposit a thick oxide layer on top of abottom gate-segment of a split gate and also on the mesa area to serveas an implant mask such the masks required for manufacturing asemiconductor power device with a split gate is reduced.

Briefly in a preferred embodiment this invention discloses a trenchedsemiconductor power device. The trenched semiconductor power deviceincludes a trenched gate, opened from a top surface of a semiconductorsubstrate, surrounded by a source region encompassed in a body regionnear the top surface above a drain region disposed on a bottom surfaceof a substrate. The semiconductor power device further includes animplanting-ion block disposed above the top surface on a mesa area nextto the body region for blocking body implanting ions and source ionsfrom entering into the substrate under the mesa area whereby masks formanufacturing the semiconductor power device can be reduced.

In an exemplary embodiment, the implanting-ion block further includes anoxide layer having a thickness larger than 0.3 micron, preferablybetween 0.5 and 1.5 micron.

In another exemplary embodiment, the implanting-ion block furtherincludes a chemical vapor deposited (CVD) oxide layer. The CVD oxide canbe deposited using LPCVD, or PECVD equipment, using Silane and Oxygengases, at reduced pressure. Atmospheric pressure APCVD techniques canalso be used to deposit the oxide.

In another exemplary embodiment, the implanting-ion block furtherincludes a thermal oxide layer. The thermal oxidation can be done attemperatures in the 900 C. to 1150 C. range, using oxygen, or oxygenwith hydrogen, and at atmospheric or enhanced pressures.

In another exemplary embodiment, the implanting-ion block furtherincludes a high-density plasma (HDP) oxide layer HDP oxide is typicallyused as a trench-fill oxide for STI (Shallow Trench Isolation), orgap-fill dielectric when planarizing multiple layers of metallization,of deep sub-micron technologies.

In another exemplary embodiment, the trenched power semiconductor powerdevice further includes a high-density plasma (HDP) deposited thickoxide layer disposed on a bottom surface of the trenched gate having athickness greater than that of a gate oxide layer which is on thesidewalls of the trenched gate. And, the implanting-ion block furtherincludes a high-density plasma (HDP) oxide layer having a thicknesslarger than 0.3 micron, preferably between 0.5 and 1.5 micron formedsimultaneously with the HDP deposited thick oxide layer disposed on thebottom surface of the trenched gate. This is possible since the HDPprocess itself results in oxide layers, which are thicker on flathorizontal surfaces, than on vertical sidewall regions or surfaces.

In another exemplary embodiment, the body region is separated astwo-separated body regions disposed on two opposite sides of thetrenched gate.

In another exemplary embodiment, the body region constituting a mergedbody region merged from two separated body regions disposed on twoopposite sides of the trenched gate having a inverted V pinnacle pointnear a bottom center of the body region.

In another exemplary embodiment, the semiconductor power device furtherincludes an insulation protective layer disposed on top of thesemiconductor power device having a plurality of contact openings openedtherethrough and extending to the body region and the semiconductorpower device further including a source/body ohmic contact dopant regiondisposed beneath each of the contact openings for enhancing ohmiccontact to the body/source region.

In another exemplary embodiment, the body region constituting a mergedbody region merged from two separated body regions disposed on twoopposite sides of the trenched gate having a inverted V pinnacle pointnear a bottom center of the body region wherein the semiconductor powerdevice having a configuration for providing a lowest breakdown voltagenear the inverted V pinnacle point for inducing a breakdown near amiddle of trenches.

In another exemplary embodiment, the semiconductor power device furtherincludes a metal oxide semiconductor field effect transistor (MOSFET)device.

In another exemplary embodiment, the semiconductor power device furtherincludes a N-channel metal oxide semiconductor field effect transistor(MOSFET) device.

In another exemplary embodiment, the semiconductor power device furtherincludes a P-channel metal oxide semiconductor field effect transistor(MOSFET) device.

In another exemplary embodiment, the semiconductor power device furtherincludes a termination area wherein the implanting-ion block having agreater width than the implanting-ion block on the mesa area forseparating the body regions and forming floating body regions in thetermination area to form at least a guard ring in a trenched gatesurrounded by the floating body region in the termination area.

In another exemplary embodiment, the semiconductor power device furtherincludes an integrated Schottky diode with a field effect transistor(FET) including a body dopant region, with a higher dopant concentrationthan the body region, disposed adjacent to the source region, and thebody dopant region having a region boundary substantially aligned withthe ion-implanting block.

In another exemplary embodiment, the trenched gate further includes asplit gate (shielded Gate) including a lower gate segment covered by aninsulation layer and an upper gate segment above the insulation layer.

In another exemplary embodiment, the trenched gate further includes asplit gate (shielded Gate) including a lower gate segment covered by aninsulation layer and an upper gate segment above the insulation layer.And, the trenched gate further including a thick oxide layer disposed ona bottom surface of the trenched gate having a thickness greater than agate oxide layer padding sidewalls of the trenched gate.

In another exemplary embodiment, the semiconductor power device furtherincludes a thick oxide layer disposed on the bottom of the trenched gateas a high-density plasma (HDP) deposited thick oxide layer and theimplanting-ion block further includes a HDP deposited oxide layer formedsimultaneously with the thick oxide layer disposed on the bottom of thetrenched gate.

This invention further discloses a method for manufacturing a trenchedsemiconductor power device. The method includes a step of opening aplurality of trenches from a top surface of a semiconductor substrateand forming a gate insulation layer on sidewalls and bottom surface ofthe trenches. The method further includes another step of forming animplanting-ion block above the top surface in a mesa area at a distanceaway from the trenches for blocking body implanting ions and source ionsfrom entering into the substrate under the mesa area whereby masks formanufacturing the semiconductor power device can be reduced.

In one exemplary embodiment, the step of forming the implanting-ionblock further includes a step of forming an oxide layer in the mesa areahaving a thickness larger than 0.3 micron, preferably between 0.5 and1.5 micron.

In another exemplary embodiment, the step of forming the implanting-ionblock further includes a step of applying a chemical vapor deposition(CVD) to form an oxide layer in the mesa area. The CVD oxide can bedeposited using LPCVD, or PECVD equipment, using Silane and Oxygengases, at reduced pressure. Atmospheric pressure APCVD techniques canalso be used to deposit the oxide

In another exemplary embodiment, the step of forming the implanting-ionblock further includes a step of applying a thermal oxidation to form anoxide layer in the mesa area The thermal oxidation can be done attemperatures in the 900 C. to 1150 C. range, using oxygen, or oxygenwith hydrogen, and at atmospheric or enhanced pressures.

In another exemplary embodiment, the step of forming the implanting-ionblock further includes a step of applying a high-density plasma (HDP)deposition process to deposit an oxide layer in the mesa area HDP oxideis typically used as a trench-fill oxide for STI (Shallow TrenchIsolation), or gap-fill dielectric when planarizing multiple layers ofmetallization, of deep sub-micron technologies.

In another exemplary embodiment, the method further includes a step ofapplying a high-density plasma (HDP) deposition process for depositing athick oxide layer on a bottom surface of the trenched gate having athickness greater than a gate oxide layer padding sidewalls of thetrenched gate. And, the method further includes another step of formingthe implanting-ion block simultaneously, by using the HDP depositionprocess for depositing a thick oxide layer on the bottom surface of thetrench, to form a HDP oxide layer as the implanting-ion block in themesa area having a thickness larger than 0.3 micron, preferably between0.5 and 1.5 micron. This is possible since the HDP process itselfresults in oxide layers, which are thicker on flat horizontal surfaces,than on vertical sidewall regions or surfaces.

In another exemplary embodiment, the method further includes a step ofimplanting body ions into the semiconductor substrate with theimplanting-ion block blocking the mesa area and diffusing the body ionsinto a body region with the body region separated as two separated bodyregions disposed on two opposite sides of the trenches.

In another exemplary embodiment, the method further includes a step ofimplanting body ions into the semiconductor substrate with theimplanting-ion block blocking the mesa area and diffusing the body ionsinto a merged body region with the body region merged from two separatedbody regions disposed on two opposite sides of the trenched gate havinga inverted V pinnacle point near a bottom center of the body region.

In another exemplary embodiment, the method further includes a step offorming an insulation protective layer on top of the semiconductor powerdevice and opening a plurality of contact openings therethrough andextending to a body region. And the method further includes another stepof implanting a source-body ohmic contact dopant to form a source/bodyohmic contact dopant region beneath each of the contact openings forenhancing ohmic contact to the body/source region.

In another exemplary embodiment, the method further includes a step ofimplanting body ions into the semiconductor substrate with theimplanting-ion block blocking the mesa area and diffusing the body ionsinto a merged body region with the body region merged from two separatedbody regions disposed on two opposite sides of the trenched gate havinga inverted V pinnacle point near a bottom center of the body region. Andthe method further includes another step of configuring thesemiconductor power device to have a lowest breakdown voltage near theinverted V pinnacle point for inducing a breakdown near a bottom of thebody region.

These and other objects and advantages of the present invention will nodoubt become obvious to those of ordinary skill in the art after havingread the following detailed description of the preferred embodiment,which is illustrated in the various drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1G are cross sectional views for describing themanufacturing processes in applying a new HDP process to form thetrenched MOSFET devices of this invention with reduced number of masks.

FIG. 2 is a cross sectional view of a MOSFET device for illustrating theconfiguration of the guard rings in the termination area for a MOSFETdevice of shown in FIG. 1.

FIGS. 3A to 3C are cross sectional views for describing themanufacturing processes by applying a new HDP process to form a trenchedMOSFET device of this invention with thick oxide with embedded SchottkyFET with reduced number masks.

FIGS. 4A to 4E are a series of cross sectional views for describing themanufacturing processes by applying a new HDP process to form a trenchedMOSFET device of this invention with split gate and thick oxide layer onthe trench bottom by using reduced number masks.

FIGS. 5A to 5E are a series of cross sectional views for describing themanufacturing processes by applying a new HDP process to form a trenchedMOSFET device of this invention with split gate by using reduced numbermasks.

FIGS. 6A to 6C are a series of cross sectional views for describing themanufacturing processes by applying a new process to form a trenchedMOSFET device of this invention with reduced number of masks by using animplanting-ion blocks on the mesa areas in the MOSFET device.

DETAILED DESCRIPTION OF THE METHOD

Referring to FIGS. 1A to 1G for a series of cross sectional views fordescribing the manufacturing processes of a new and improved trenchMOSFET device of this invention. In FIG. 1A, a first mask (not shown) isfirst applied to open a plurality of trenches 108 into an epitaxiallayer 110 supported on a semiconductor substrate 105. Then ahigh-density plasma (HDP) oxide layer is applied to form a thick oxidelayer 115 at the trench bottom and thinner oxide layer 119 on trenchsidewalls and thicker oxide layer 120 on the top surface of thesubstrate. In FIG. 1B, an oxide wet etch is carried out to etch out thethinner oxide layer 119 surrounding the sidewalls of the trench 108 andalso a part of the thick oxide layer 120 near the trenches 108 andleaving only the thick oxide layer 120 in the mesa area and the thickeroxide layer 115 on the trench bottom. In FIG. 1C, a gate oxide layer 125is then formed by thermal oxidation followed with filling the trenches108 with polysilicon and etch back to form the polysilicon gate 130 inthe trenches. Alternatively gate oxide 125 may be formed by deposition,preferably using HTO (high temperature oxide) techniques by mixingdicholorosilane with oxygen, at reduced pressure, in the range of700-900 C., resulting a conformal oxide deposition layer over the trenchsidewall, as well as the remaining HDP oxide. Gate oxide thickness canbe in the 100A to 1500A range, or more, depending on the desiredgate-source voltage rating for the transistor.

In FIG. 1D, a body implant is performed followed by a diffusionoperation to drive the body region 135 into the epitaxial layer 110.Alternatively, the body implant may be carried out with angled androtated implant before gate oxide layer 125 is formed, using oxideregion 120 on top of the mesa and oxide region 115 on the trench bottomas a mask. One advantage of this later approach is the body does notneed to drive as far as the previous approach, therefore the lateraldiffusion is less and the body region can be narrower, thus the cellscan be packed tighter. Then a source implant is performed followed by asource region drive operation to form the source regions 140. As shownin FIG. 1D, with the thicker oxide layer 120 disposed in the mesa areas,the body and source implant operations are carried out without requiringimplant masks thus achieve manufacturing process simplification and costsavings.

In one embodiment, the thick oxide 120 blocks the body implant that thetwo body regions under each side of oxide 120 are completely separatedafter diffusion (not shown); in another embodiment, the two body regionsmerge together after diffusion forming an inverted V shape profile inthe merging area in the middle of the two trenches, as shown in FIG. 1D.The vertical position of the inverted V pinnacle point can be carefullycontrolled by adjusting the mesa width, the implant energy and diffusiondepth.

In FIG. 1E, insulation layer 145, e.g., LTO oxide layer and BPSG layer,is deposited on the top surface. In FIG. 1F, a third mask (not shown) isapplied to open a plurality of source and gate contact openings 150-Sand 150-G respectively. A P+ contact region 155 is implanted thenactivated at elevated temperature to form source/body metal ohmiccontact and gate metal ohmic contact through the layer 145. In FIG. 1G,the manufacturing processes are then completed with metal layerdeposition and patterning on the top surface to form the source metal160-S and gate pad 160-G and backside metal contact formation for drainconnection 170 to the MOSFET 100 device.

A new and improved manufacturing process is disclosed with the MOSFET100 shown above that has thicker oxide layer at the bottom of the trenchgate and is manufactured with only three masks. The MOSFET devicefurther has a new structure wherein the thick oxide layer 115 at thebottom of the trench gate is formed by HDP oxide as the HDP oxide layer120 in the mesa area. By controlling the mesa width, the body depth andthe P+ contact implant regions 155, a high electric filed may be createdbetween the bottom of P+ contact implant 155 and the inverted V pinnaclepoint so that the breakdown at this region will occur before other areareach breakdown voltage.

Referring to FIG. 2 for a cross sectional view of a MOSFET device forillustrating the configuration of the guard rings in the terminationarea for a MOSFET device 100 shown in FIG. 1. For the purpose of formingthe guard rings to sustain higher voltages, the spacing between thetrenches 130′ in the termination area is increased to have a wider spacebetween the trench gates 130′ and consequently the body regions 135′ areformed as separated floating regions as shown to provide the guardingring protection functions. If necessary, a separate mask may be appliedto block the n+ implant into the guard ring areas and that wouldincrease the number of masks to four as required for manufacturing theMOSFET device with guard rings that are different from FIG. 2 withoutthe n+ regions 140.

Referring to FIGS. 3A to 3C for a series of cross sectional views fordescribing the manufacturing processes by applying a new HDP process toform a trenched MOSFET device of this invention with thick oxide atbottom of trench gate and with embedded Schottky diode. The new methodenables the manufacture of such device with reduced number masks.Referring to FIGS. 1A to 1D for the processing steps by applying a firstmask to complete the manufacturing processes for a partially completeddevice as shown in FIG. 3A. The only exception is that the body regions135 in FIG. 3A are formed as separated body regions instead of mergingtogether as that shown in FIG. 1D. In FIG. 3B, a second mask 123 isapplied as a contact block mask to pull back the HDP surface oxide layer120 followed by a P+ contact implant to form the contact implant regions148.

The manufacturing processes proceed by first removing the contact blockmask 123 and the deposition of insulation layers of LTO/BPSG thenapplying a third mask as a contact mask to open the metal contactopenings through the insulation layers. After BPSG reflow a Schottkybarrier 170 followed by a metal layer 160 is deposited and patterned assource pad and gate pad as that shown and described in FIGS. 1E to 1Gabove. The final structure as shown in FIG. 3C is therefore completedwith four masks that has a MPS (Merged PIN/Schottky) or JBS (junctionbarrier shcottky) rectifier within each cell. Specifically, the Schottkybarrier layer 170, the P body regions 135 and the N-epi region betweenthe separated P body regions configuring a MPS/JBS that greatly reducesthe voltage drop over the MOSFET body diode in reverse conducting mode.

Referring to FIGS. 4A to 4E for a series of cross sectional views fordescribing the manufacturing processes by applying a new HDP process toform a trenched MOSFET device of this invention with split gate andthick oxide layer on the trench bottom by using reduced number masks. InFIG. 4A, a first mask (not shown) is first applied to open a pluralityof trenches 208 into an epitaxial layer 210 supported on a semiconductorsubstrate 205. Then a high-density plasma deposition (HDP) of oxidelayer is applied to form a thick oxide layer 215 at the trench bottomand thinner oxide layer 219 and thicker oxide layer 220 on the topsurface of the substrate. In FIG. 4B, a deposition of first polysilicongate and etch back of the polysilicon is carried out to form the bottomsegment of the gate 225 at the bottom portion of the trenches 208. InFIG. 4C, a second high-density plasma deposition (HDP) oxide layer iscarried out to deposit a second oxide layer 230 on top of the first HDPoxide layer 215 and the first gate segment 225. In FIG. 4D, an oxideetch is carried out to etch out part of the oxide layers 230 and theupper portion of thinner oxide 219 surrounding the sidewalls of thetrench 208. The oxide etch also removes the second HDP layer 230 and apart of the thick oxide layer 220 near the trenches 208 and leaving onlythick oxide layer 220 in the mesa area and the thick second HDP oxidelayer 230 on top of the bottom gate segment. In FIG. 4E, the split gateis formed by a depositing a second polysilicon layer 240 followed by apolysilicon etch back to form the upper gate segment 240 on top of theinter-poly insulation layer 230 formed by the second HDP oxidedeposition process. After the formation of the split gate, the MOSFETmanufacturing processes proceed according to the steps as that describedin FIGS. 1D to 1G.

Referring to FIGS. 5A to 5E for a series of cross sectional views fordescribing the manufacturing processes by applying a new HDP process toform a trenched MOSFET device of this invention with split gate by usingreduced number masks. The manufacturing processes are similar to thatdescribed for FIGS. 4A to 4E. The only differences are shown in FIGS. 5Aand 5B where normal thermal oxide layer 215′ with uniform thickness isformed on the trench bottom without applying a HDP oxide deposition toform the thick trench bottom oxide 215 as shown in FIGS. 4A and 4B. Theremainder of the processing steps as shown in FIGS. 5C to 5E arebasically identical to that shown in FIGS. 4C to 4E with the exceptionthat the thick oxide layer 230 in the mesa area is formed by the onlyHDP oxide deposition since unlike the processes shown in FIGS. 4A to 4E,there is only one HDP oxide deposition process. Therefore, the MOSFETdevice with split gates can be manufactured with reduced number of masksby taking advantage of the HDP oxide deposition process that is provideto form oxide layer with different thickness in different targetedareas.

The goal to reduce the mask count in MOSFET manufacturing process canalso be achieved using regular thermal oxidation process or CVDdeposition. FIGS. 6A-6C describe such a process. In FIG. 6A a thickoxide layer 620 is grown through thermal oxidation or CVD deposition andis used as a hard mask by applying trench mask to etch trench 608 intothe epi layer 610 overlaying substrate 605. In FIG. 6B, an oxide pullback etch is carried out to remove the oxide near the trench forming asource/body implant block. A gate is then formed within the trenchfollowing the standard process to form a split gate or a normal gatebefore the body and source are implanted. Alternatively, the body andsource implant may be carried out before the gate formation using aresist 630 to fill the trench to block source body implanting into thebottom of trench as shown in FIG. 6C. The device is then completed withthe normal manufacturing process.

Although the present invention has been described in terms of thepresently preferred embodiment, it is to be understood that suchdisclosure is not to be interpreted as limiting. Various alterations andmodifications will no doubt become apparent to those skilled in the artafter reading the above disclosure. Accordingly, it is intended that theappended claims be interpreted as covering all alterations andmodifications as fall within the true spirit and scope of the invention.

We claim:
 1. A method for manufacturing a trenched semiconductor powerdevice comprising: applying a trench mask for opening a plurality oftrenches from a top surface of a semiconductor substrate by configuringthe trench mask having a greater distance between two adjacent trenchesin a termination area than an active cell area and forming a thickinsulation layer covering over trench sidewalls and a bottom surface ofsaid trenches and also simultaneously covering over the top surface ofthe semiconductor substrate outside of the trenches; applying animplanting-ion block mask for etching the thick insulation layer from atop part of the trenches and the trench sidewalls and alsosimultaneously from an area surrounding the trenches thus leaving athick bottom insulation layer at a bottom portion of the trenches andimplanting-ion blocks above said top surface in a mesa area between andat a distance away from said trenches and in a middle portion betweentwo of said trenches for blocking body implanting ions and source ionsfrom entering into said substrate under said mesa area whereby masks formanufacturing said semiconductor power device can be reduced; andimplanting body dopant ions and source dopant ions with saidimplanting-ion block blocking said mesa area in the middle portionbetween two of said trenches to form body regions encompassing sourceregions and forming the body regions in the termination area as floatingbody regions to function as guard rings for the semiconductor powerdevice.
 2. The method of claim 1 wherein: the step of forming the thickinsulation layer further comprising a step of forming an oxide layerhaving a thickness larger than 0.3 microns.
 3. The method of claim 1wherein: the step of forming the thick insulation layer furthercomprising a step of applying a HDP deposition process to form an HDPoxide layer covering over trench sidewalls and the bottom surface ofsaid trenches and also covering over the top surface of thesemiconductor substrate outside of the trenches.
 4. The method of claim1 wherein: the step of forming the thick insulation layer furthercomprising a step of applying a high-density plasma (HDP) depositionprocess for depositing a thick oxide layer covering a bottom surface ofsaid trenches and also covering over the top surface of thesemiconductor substrate outside of the trenches having a thicknesslarger than 0.3 microns and greater than a thickness of the insulationlayer covering the trench sidewalls having a thickness larger than 0.3microns and greater than a thickness of the insulation layer coveringthe trench sidewalls.
 5. The method of claim 1 wherein: the step offorming the thick insulation layer further comprising a step of applyinga chemical vapor deposition (CVD) to form an oxide layer covering overtrench sidewalls and the bottom surface of said trenches and alsocovering over the top surface of the semiconductor substrate outside ofthe trenches.
 6. The method of claim 1 wherein: the step of forming saidthick insulation layer further comprising a step of applying a thermaloxidation to form an oxide layer covering over trench sidewalls and thebottom surface of said trenches and also covering over the top surfaceof the semiconductor substrate outside of the trenches.
 7. A method formanufacturing a trenched semiconductor power device comprising: applyinga trench mask for opening a plurality of trenches from a top surface ofa semiconductor substrate by configuring the trench mask having agreater distance between two adjacent trenches in a termination areathan an active cell area and forming a thick insulation layer coveringover trench sidewalls and a bottom surface of said trenches and alsosimultaneously covering over the top surface of the semiconductorsubstrate outside of the trenches; applying an implanting-ion block maskfor etching the thick insulation layer from a top part of the trenchesand the trench sidewalls and also simultaneously from an areasurrounding the trenches thus leaving a thick bottom insulation layer ata bottom portion of the trenches and implanting-ion blocks above saidtop surface in a mesa area between and at a distance away from saidtrenches and in a middle portion between two of said trenches forblocking body implanting ions and source ions from entering into saidsubstrate under said mesa area whereby masks for manufacturing saidsemiconductor power device can be reduced; and implanting body dopantions with said implanting-ion block and followed by applying a sourceion implant mask for implanting source dopant ions to form body regionsencompassing source regions adjacent to the mesa area in the middleportion between two of said trenches and forming the body regions in thetermination area as floating body regions and having no source regionstherein to function as guard rings for the semiconductor power device.8. The method of claim 7 wherein: the step of forming the thickinsulation layer further comprising a step of forming an oxide layerhaving a thickness larger than 0.3 microns.
 9. The method of claim 7wherein: the step of forming the thick insulation layer furthercomprising a step of applying a HDP deposition process to form an HDPoxide layer covering over trench sidewalls and the bottom surface ofsaid trenches and also covering over the top surface of thesemiconductor substrate outside of the trenches.
 10. The method of claim7 wherein: the step of forming the thick insulation layer furthercomprising a step of applying a high-density plasma (HDP) depositionprocess for depositing a thick oxide layer covering bottom surface ofsaid trenches and also covering over the top surface of thesemiconductor substrate outside of the trenches having a thicknesslarger than 0.3 microns and greater than a thickness of the insulationlayer covering the trench sidewalls having a thickness larger than 0.3microns and greater than a thickness of the insulation layer coveringthe trench sidewalls.
 11. The method of claim 7 wherein: the step offorming the thick insulation layer further comprising a step of applyinga chemical vapor deposition (CVD) to form an oxide layer covering overtrench sidewalls and the bottom surface of said trenches and alsocovering over the top surface of the semiconductor substrate outside ofthe trenches.
 12. The method of claim 7 wherein: the step of formingsaid thick insulation layer further comprising a step of applying athermal oxidation to form an oxide layer covering over trench sidewallsand the bottom surface of said trenches and also covering over the topsurface of the semiconductor substrate outside of the trenches.
 13. Amethod for manufacturing a trenched semiconductor power devicecomprising: applying a trench mask for opening a plurality of trenchesfrom a top surface of a semiconductor substrate by configuring thetrench mask having a greater distance between two adjacent trenches in atermination area than an active cell area and forming a thick insulationlayer covering over trench sidewalls and a bottom surface of saidtrenches and also simultaneously covering over the top surface of thesemiconductor substrate outside of the trenches; applying animplanting-ion block mask for etching the thick insulation layer from atop part of the trenches and the trench sidewalls and alsosimultaneously from an area surrounding the trenches thus leaving athick bottom insulation layer at a bottom portion of the trenches andimplanting-ion blocks above said top surface in a mesa area between andat a distance away from said trenches and in a middle portion betweentwo of said trenches for blocking body implanting ions and source ionsfrom entering into said substrate under said mesa area whereby masks formanufacturing said semiconductor power device can be reduced; andimplanting P-type body dopant ions with said implanting-ion block andfollowed by applying a source ion implant mask for implanting N-typesource dopant ions to form P-type body regions encompassing N-typesource regions adjacent to the mesa area with said implanting-ion blockand forming the P-type body regions in the termination area as floatingbody regions and having no source regions therein to function as guardrings for the semiconductor power device.
 14. The method of claim 13wherein: the step of forming the thick insulation layer furthercomprising a step of forming an oxide layer having a thickness largerthan 0.3 microns.
 15. The method of claim 13 wherein: the step offorming the thick insulation layer further comprising a step of applyinga HDP deposition process to form an HDP oxide layer covering over trenchsidewalls and the bottom surface of said trenches and also covering overthe top surface of the semiconductor substrate outside of the trenches.16. The method of claim 13 wherein: the step of forming the thickinsulation layer further comprising a step of applying a high-densityplasma (HDP) deposition process for depositing a thick oxide layercovering bottom surface of said trenches and also covering over the topsurface of the semiconductor substrate outside of the trenches having athickness larger than 0.3 microns and greater than a thickness of theinsulation layer covering the trench sidewalls having a thickness largerthan 0.3 microns and greater than a thickness of the insulation layercovering the trench sidewalls.
 17. The method of claim 13 wherein: thestep of forming the thick insulation layer further comprising a step ofapplying a chemical vapor deposition (CVD) to form an oxide layercovering over trench sidewalls and the bottom surface of said trenchesand also covering over the top surface of the semiconductor substrateoutside of the trenches.
 18. The method of claim 13 wherein: the step offorming said thick insulation layer further comprising a step ofapplying a thermal oxidation to form an oxide layer covering over trenchsidewalls and the bottom surface of said trenches and also covering overthe top surface of the semiconductor substrate outside of the trenches.